a(0)=1, a(1)=0, a(n) = a(n-1) + a(n-2) + Sum_{i=0...n-1} a(i).

Terms

a(0) =1a(1) =0a(2) =2a(3) =5a(4) =15a(5) =43a(6) =124a(7) =357a(8) =1028a(9) =2960a(10) =8523a(11) =24541a(12) =70663a(13) =203466a(14) =585857a(15) =1686908a(16) =4857258a(17) =13985917a(18) =40270843a(19) =115955271a(20) =333879896a(21) =961368845a(22) =2768151264a(23) =7970573896a(24) =22950352843a(25) =66082907265a(26) =190278147899a(27) =547884090854